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Date: Fri, 18 Aug 2017 13:46:17 +0200
From: Michal Hocko <mhocko@...nel.org>
To: Григорий Резников
<grikukan@...l.ru>
Cc: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
linux-api@...r.kernel.org
Subject: Re: [PATCH] Adding support of RLIMIT_CPUNS
Appart from Andrew said about the usecase make sure to CC linux-api for
any user visible interface change.
On Thu 17-08-17 22:45:45, Григорий Резников wrote:
> To set time limit for process now we can use RLIMIT_CPU.
> However, it has precision up to one second and it can be
> too big for some purposes.
>
> This patch adds support of RLIMIT_CPUNS, which works
> almost as RLIMIT_CPU, but has nanosecond precision.
>
> At the moment, RLIMIT_CPU and RLIMIT_CPUNS are two
> independent values, because I don't see any nice way
> for them to be together.
>
> Signed-off-by: Grigory Reznikov <grikukan@...l.ru>
> ---
> fs/proc/base.c | 1 +
> include/asm-generic/resource.h | 1 +
> include/linux/posix-timers.h | 1 +
> include/uapi/asm-generic/resource.h | 4 +++-
> kernel/fork.c | 20 +++++++++++++----
> kernel/sys.c | 11 ++++++++-
> kernel/time/posix-cpu-timers.c | 45 +++++++++++++++++++++++++++++++++----
> 7 files changed, 73 insertions(+), 10 deletions(-)
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 719c2e9..1e3049e 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -567,6 +567,7 @@ static const struct limit_names lnames[RLIM_NLIMITS] = {
> [RLIMIT_NICE] = {"Max nice priority", NULL},
> [RLIMIT_RTPRIO] = {"Max realtime priority", NULL},
> [RLIMIT_RTTIME] = {"Max realtime timeout", "us"},
> + [RLIMIT_CPUNS] = {"Max cpu time", "ns"},
> };
>
> /* Display limits for a process */
> diff --git a/include/asm-generic/resource.h b/include/asm-generic/resource.h
> index 5e752b9..ec7b0c5 100644
> --- a/include/asm-generic/resource.h
> +++ b/include/asm-generic/resource.h
> @@ -25,6 +25,7 @@
> [RLIMIT_NICE] = { 0, 0 }, \
> [RLIMIT_RTPRIO] = { 0, 0 }, \
> [RLIMIT_RTTIME] = { RLIM_INFINITY, RLIM_INFINITY }, \
> + [RLIMIT_CPUNS] = { RLIM_INFINITY, RLIM_INFINITY }, \
> }
>
> #endif
> diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
> index 62839fd..0e22bde 100644
> --- a/include/linux/posix-timers.h
> +++ b/include/linux/posix-timers.h
> @@ -110,6 +110,7 @@ void posix_cpu_timers_exit_group(struct task_struct *task);
> void set_process_cpu_timer(struct task_struct *task, unsigned int clock_idx,
> u64 *newval, u64 *oldval);
>
> +void update_rlimit_cpu_ns(struct task_struct *task, unsigned long rlim_new);
> void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new);
>
> void posixtimer_rearm(struct siginfo *info);
> diff --git a/include/uapi/asm-generic/resource.h b/include/uapi/asm-generic/resource.h
> index c6d10af..a86b2f4 100644
> --- a/include/uapi/asm-generic/resource.h
> +++ b/include/uapi/asm-generic/resource.h
> @@ -45,7 +45,9 @@
> 0-39 for nice level 19 .. -20 */
> #define RLIMIT_RTPRIO 14 /* maximum realtime priority */
> #define RLIMIT_RTTIME 15 /* timeout for RT tasks in us */
> -#define RLIM_NLIMITS 16
> +#define RLIMIT_CPUNS 16 /* CPU time in ns,
> + doesn't depend on RLIMIT_CPU */
> +#define RLIM_NLIMITS 17
>
> /*
> * SuS says limits have to be unsigned.
> diff --git a/kernel/fork.c b/kernel/fork.c
> index e075b77..33f9bbf 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1348,11 +1348,23 @@ void __cleanup_sighand(struct sighand_struct *sighand)
> */
> static void posix_cpu_timers_init_group(struct signal_struct *sig)
> {
> - unsigned long cpu_limit;
> -
> + unsigned long cpu_limit, cpuns_limit, total_limit;
> + /* RLIMIT_CPU timeout, RLIMIT_CPUNS timeout and time
> + * to closest timeout
> + */
> +
> cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
> - if (cpu_limit != RLIM_INFINITY) {
> - sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC;
> + cpuns_limit = READ_ONCE(sig->rlim[RLIMIT_CPUNS].rlim_cur);
> +
> + total_limit = RLIM_INFINITY;
> +
> + if (cpu_limit != RLIM_INFINITY)
> + total_limit = cpu_limit * NSEC_PER_SEC;
> + if (cpuns_limit != RLIM_INFINITY && cpuns_limit < total_limit)
> + total_limit = cpuns_limit;
> +
> + if (total_limit != RLIM_INFINITY) {
> + sig->cputime_expires.prof_exp = total_limit;
> sig->cputimer.running = true;
> }
>
> diff --git a/kernel/sys.c b/kernel/sys.c
> index 2855ee7..539b110 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -1504,6 +1504,8 @@ int do_prlimit(struct task_struct *tsk, unsigned int resource,
> */
> new_rlim->rlim_cur = 1;
> }
> + if (resource == RLIMIT_CPUNS && new_rlim->rlim_cur == 0)
> + new_rlim->rlim_cur = NSEC_PER_SEC;
> }
> if (!retval) {
> if (old_rlim)
> @@ -1519,10 +1521,17 @@ int do_prlimit(struct task_struct *tsk, unsigned int resource,
> * very long-standing error, and fixing it now risks breakage of
> * applications, so we live with it
> */
> - if (!retval && new_rlim && resource == RLIMIT_CPU &&
> + if (!retval && new_rlim && resource == RIMIT_CPU &&
> new_rlim->rlim_cur != RLIM_INFINITY &&
> IS_ENABLED(CONFIG_POSIX_TIMERS))
> update_rlimit_cpu(tsk, new_rlim->rlim_cur);
> +
> + if (!retval && new_rlim && resource == RLIMIT_CPUNS &&
> + new_rlim->rlim_cur != RLIM_INFINITY &&
> + IS_ENABLED(CONFIG_POSIX_TIMERS))
> + update_rlimit_cpu_ns(tsk, new_rlim->rlim_cur);
> +
> +
> out:
> read_unlock(&tasklist_lock);
> return retval;
> diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
> index a3bd5db..e4830f6 100644
> --- a/kernel/time/posix-cpu-timers.c
> +++ b/kernel/time/posix-cpu-timers.c
> @@ -19,20 +19,26 @@
> static void posix_cpu_timer_rearm(struct k_itimer *timer);
>
> /*
> - * Called after updating RLIMIT_CPU to run cpu timer and update
> + * Called after updating RLIMIT_CPUNS to run cpu timer and update
> * tsk->signal->cputime_expires expiration cache if necessary. Needs
> * siglock protection since other code may update expiration cache as
> * well.
> */
> -void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
> +void update_rlimit_cpu_ns(struct task_struct *task, unsigned long rlim_new)
> {
> - u64 nsecs = rlim_new * NSEC_PER_SEC;
> + u64 nsecs = rlim_new;
>
> spin_lock_irq(&task->sighand->siglock);
> set_process_cpu_timer(task, CPUCLOCK_PROF, &nsecs, NULL);
> spin_unlock_irq(&task->sighand->siglock);
> }
>
> +/* Same function for RLIMIT_CPU */
> +void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
> +{
> + update_rlimit_cpu(task, rlim_new * NSEC_PER_SEC);
> +}
> +
> static int check_clock(const clockid_t which_clock)
> {
> int error = 0;
> @@ -938,6 +944,9 @@ static void check_process_timers(struct task_struct *tsk,
> SIGPROF);
> check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
> SIGVTALRM);
> + /*
> + * RLIMIT_CPU check
> + */
> soft = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
> if (soft != RLIM_INFINITY) {
> unsigned long psecs = div_u64(ptime, NSEC_PER_SEC);
> @@ -974,7 +983,35 @@ static void check_process_timers(struct task_struct *tsk,
> if (!prof_expires || x < prof_expires)
> prof_expires = x;
> }
> -
> + /*
> + * RLIMIT_CPUNS check
> + */
> + soft = READ_ONCE(sig->rlim[RLIMIT_CPUNS].rlim_cur);
> + if (soft != RLIM_INFINITY) {
> + unsigned long hard =
> + READ_ONCE(sig->rlim[RLIMIT_CPUNS].rlim_max);
> + if (ptime >= hard) {
> + if (print_fatal_signals) {
> + pr_info("RT Watchdog Timeout (hard): %s[%d]\n",
> + tsk->comm, task_pid_nr(tsk));
> + }
> + __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
> + return;
> + }
> + if (ptime >= soft) {
> + if (print_fatal_signals) {
> + pr_info("CPU Watchdog Timeout (soft): %s[%d]\n",
> + tsk->comm, task_pid_nr(tsk));
> + }
> + __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
> + if (soft < hard) {
> + soft += NSEC_PER_SEC;
> + sig->rlim[RLIMIT_CPUNS].rlim_cur = soft;
> + }
> + }
> + if (!prof_expires || soft < prof_expires)
> + prof_expires = soft;
> + }
> sig->cputime_expires.prof_exp = prof_expires;
> sig->cputime_expires.virt_exp = virt_expires;
> sig->cputime_expires.sched_exp = sched_expires;
> --
> 2.7.4
--
Michal Hocko
SUSE Labs
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